170 



FLUORESCENCE OF THE URANYL SALTS. 



(3) The fluorescence groups are distinguished by a strong pair of 

 bands, fairly dominant in all the spectra excepting that of the sodium 

 salt. The series formed by the members of shorter wave-length of 

 these pairs terminates toward the violet, where it meets the head of 

 the corresponding absorption series mentioned above. 



(4) The location in the spectrum of the fluorescence groups in the 

 spectrum of the sulphates is not approximately the same for the 

 different salts, as is the case with the corresponding double acetates. 

 On the contrary, there is in general a shift toward the violet with 

 increasing molecular weight, as may be seen from figure 88, in which 

 group 5 of the 6 sulphates under consideration are depicted. This 

 shift is larger than that observed in the double nitrates, but not 

 quite so systematic. 



TABLE 99. Uranyl sulphate: U0 2 .SO*3HzO. Fluorescence at 185 C. 



Prepared by extracting an excess of uranium oxide (UsOs) with sulphuric acid and oxidiz- 

 ing the solution to UC>2 . SO* by means of B^Oj. This neutral solution was evaporated to crys- 

 tallization. The crystals were needles, some being 1 by 2 by 5 mm. in size, apparently ortho- 

 rhombic, with three good pinacoidal cleavages. The angle of the optical axes is very nearly 90 

 and the double refraction is positive. 



